Refactor: objects placing in editor
Added a comment
Player warps up when too low in camera
Added a comment
Camera doesn't warp up with players
Destroy wall if it leaves the view on the top edge
Level is generated randomly
Counts and draws score for individual players
Added lines to show dangerous and safe area
Added yellow sprite for player 2
F4 toggles fullscreen; minor reordering of elements

F4 toggles fullscreen using object `obj_ctrl_fullscreen`.
Grouped all control objects in group `ctrl`.
Generalized `obj_ctrl_fullscreen` to all hotkeys
Added hotkeys for quit (Esc) and reset (F2)
Turned `obj_ctrl_hotkeys` explicitly invisible
Moved rim drawing to a separate object

Moved rim drawing functionality from `obj_control` to new
`obj_ctrl_rim`.
Moved draw objects to a separate group `draw`
Renamed `obj_ctrl_rim` to `obj_draw_rim`

This represents its functionality more properly.
Turned `obj_control` explicitly invisible
Set score display color to black
Refactor: controls are now handled in `obj_pl`